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Homework Help: Compute the surface charge density on the belt

  1. May 5, 2009 #1
    I need the answer to this question

    A charge belt, 50cm wide, travels at 40m/s between a source of charge and a charging object at a rate corresponding to 100microA . Compute the surface charge density on the belt

    Some one told me the answer may be 5 microC/m2 but how ??
  2. jcsd
  3. May 5, 2009 #2
    Re: Help

    You will need to put in some effort if you want help. For example, list some of the equations you have been trying and show some work.
  4. May 5, 2009 #3
    Re: Help

    I try this but i dont no if it is right
    J=I/A=100*10^-9 /0.5*1
    also J=(ne) V
    then ne(q)=J/v
    and then i take the q as the surface charge density
    and it well = 5*10^-9
  5. May 5, 2009 #4
    Re: Help

    The units do not come out right at all in that last equation.

    You know the current and that is just dq/dt. That is the same as saying dq charge passes by in a time dt. So draw a picture of how much charge passes by in a time dt, knowing the width of the belt and how fast it is moving.
  6. May 6, 2009 #5
    Re: Help

    Thanx Nickjer For your help I finally get it
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